Portable data storage cartridges provided convenient and low cost means for storing data. One example comprises automated data storage libraries which can contain large quantities of portable data storage cartridges on storage shelves, and employ robot accessors to access a cartridge when needed and deliver the cartridge to a data storage drive or transfer station.
In some instances, data, once recorded on a data storage medium of a portable data storage cartridge, is intended to be archived and left unchanged. Hence, a “write protect” device is placed in the cartridge which may be adjusted to indicate whether the data storage medium is write enabled and can be erased and written over, or whether the data storage medium is write protected and is not to be erased, as detected by a switch at the data storage drive which accepts the cartridge. Examples of two-position “on-off” write protect devices for magnetic tape media in which one position is the same as though no cartridge is present are illustrated in U.S. Pat. No. 4,320,421, Larson et al., U.S. Pat. No. 4,399,481, Loranger et al., U.S. Pat. No. 5,699,216, Doty, and U.S. Pat. No. 5,786,967, Gerfast et al. Gerfast et al. arranges the size of a recess and the write protect device such that separate switches of the data storage drive that are for detecting the presence of a cartridge may also be utilized with the write protect switch to write protect magnetic tape having a different coercivity from being written by an older tape drive, and to selectively write protect the tape in a newer tape drive. Thus, Gerfast et al. provides a same as though no cartridge is present.
The incorporated '188 U.S. patent application provides an encoded multi-position mechanical indicator for a portable data storage cartridge in which the indicator comprises a rotary device in the form of a right cylinder arranged to be rotatable in a chamber of a portable data storage cartridge, which has an exterior wall opening to the chamber. A peripheral surface of the rotary device has an encoded pattern of at least one cylindrical surface and a plurality of facets interrupting the cylindrical surface(s). The facets are located at various axial positions, and at various angularly spaced rotational positions, such that, at differing rotational positions of the rotary device, at least one or none of the facets is positioned at the exterior opening. This allows additional information rather than the simple binary “write-protect” to be encoded in the indicator.
The specific set of encoded information for each position of the indicator must be provided in advance and encoded into the indicator, e.g., as facets and cylindrical surfaces. As an example, the encoded pattern may be represented in binary terms, with the cylindrical surface comprising a “1” and activating a switch, and a facet comprising a “0” and not activating a switch. Thus, a three-sided encoded pattern, reading from top to bottom of the rotary device, respectively, might represent “0–1 ”, “1–0” and “1—1”. A fourth code of “0—0” would require adding a fourth side with both an upper facet and a lower facet positioned at the exterior wall opening of the portable data storage cartridge, or one of the other codes could be eliminated.